Multi-chamber installation for treating objects under vacuum, method for evacuating said installation and evacuation system therefor

ABSTRACT

A multi-chamber installation ( 1 ) treats objects under vacuum. An evacuation system ( 5 ) is connected to a plurality of chambers ( 2, 3, 4 ). To reduce the complexity of the evacuation process, a forepump ( 5 ) has several stages ( 11, 12, 13 ). Each of said stages is connected to one of the chambers ( 2, 3, 4 ).

BACKGROUND OF THE INVENTION

The invention relates to a multi-chamber installation for treatingobjects under vacuum, in which an evacuation system that is connected tothe chambers. Moreover, the present invention relates to a method forevacuating said installation as well as an evacuation system therefor.

Multi-chamber installations of the aforementioned kind are known. Theyserve the purpose of degassing, coating (metallization, for example) oretching substrates. Known methods of this kind include chemical vapordeposition (CVD). and processes for producing digital video disks(DVDs). Commonly, such an installation is equipped with a processchamber, with one or several pre-chambers with load lock function beinglocated upstream. The load locks are opened for the period of time whileintroducing or removing substrates, so that high pressure variationsoccur differing from chamber to chamber.

In the instance of a multi-chamber installation equipped with twochambers, it is known to employ two separate vacuum pumps in order to beable to evacuate as rapidly as possible each of the chambers afterclosing the corresponding load lock.

It is the task of the present invention to reduce in the instance ofmulti-chamber installations of the aforementioned kind or similar kind,the complexity for the evacuation system.

SUMMARY OF THE INVENTION

This task is solved by the present invention through the characteristicfeatures of the patent claims.

In that each of the stages is equipped with an inlet and in that each ofthe inlets is connected to one of the chambers, now only one vacuum pumpis required in order to produce the desired pressures—be theyapproximately the same or also different—in the different chambers asrapidly as possible and maintain these. Several pumps each with a drivemotor are no longer required. Also installation complexity—bothmechanical and also electrical—is reduced. Preferably the pump stagesare operated in parallel so that they have the function of twoindependent vacuum pumps.

An exemplary oil-sealed rotary vane forevacuum pump is illustrated inU.S. Pat. No. 5,156,532.

Typical forevacuum pumps are oil-sealed rotary vane pumps as they areknown, for example, from DE-U-90 07 544.

Further advantages and details of the present invention shall beexplained with reference to the examples of embodiments depictedschematically in drawing FIGS. 1 to 4.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take form in various components and arrangements ofcomponents, and in various steps and arrangements of steps. The drawingsare only for purposes of illustrating the preferred embodiments and arenot to be construed as limiting the invention.

FIG. 1 depicts a multi-chamber installation with three chambers and athree stage forevacuum pump,

FIG. 2 depicts a multi-chamber installation with two vacuum chambers anda two-stage forevacuum pump,

FIG. 3 depicts a multi-chamber installation according to drawing FIG. 2with an additional high vacum pump, and

FIG. 4 depicts a sectional view through a two-stage forevacum pump.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the drawing figures, the multi-chamber installation is generallydesignated as 1, the chambers with 2, 3 and 4, and the evacuation systemwith 5. In the instance of the chambers 2 to 4, these each include aprocess chamber 2, to which further chambers 3, 4, (in drawing FIG. 1)or only 4 (in drawing FIG. 2, 3) are associated. Slotted load locks areschematically depicted and designated as 6, 7, and 8. The evacuationsystem 5 is designed as a multi-stage forevacuum pump.

In the example of the embodiment in accordance with drawing FIG. 1,three chambers 2, 3, 4 are present. Correspondingly, the forevacuum pump5 has three stages 11, 12, 13 each with one inlet 14, 15, respectively16. Each of the inlets 14, 15, 16 is connected via one each connectingline 17, 18, respectively in 19 to one of the chambers 2, 3, 4. Theoutlets 20, 21, 22 of the pump stages 11, 12, 13 open out within thepump 5 into a joint discharge line, so that the pump 5 has only oneoutlet 23. In the instance of the pumping stages 11, 12, 13 havingdifferent pumping capacities, it is then expedient to connect the stagewith the highest pumping capacity to the process chamber 2, so thatthere sufficiently low pressures are attainable as rapidly as possible.

In the embodiment according to drawing FIG. 2, only two chambers 2, 4and correspondingly two pump stages 11, 13 are provided. Located in theconnecting lines 17 and 19 are valves 24 and 25 in order to separatefrom the evacuation system 5 one or both chambers 2, 4 in case these arevented.

In the embodiment according to drawing FIG. 3, there is located in theconnecting line 17 a turbomolecular vacuum pump 26 and—on its deliveryside—a valve 27. High vacuum pumps of this kind excel through higherpumping capacities and lower ultimate pressures compared to forevacuumpumps, however, they require a forevacuum pump which in the instance ofthe case presented, forms the pumping stage 11. This embodiment isexpedient for processes being performed in the process chamber 2 inwhich relatively low pressures (10⁻² mbar, for example) shall beattained as rapidly as possible. Forevacuum pumps are also capable ofattaining ultimate pressures of approximately 1 mbar to 5×10⁻² mbar;however, through the utilisation of high vacuum pumps it is possible toattain even lower pressures significantly faster.

Drawing FIG. 4 depicts a partial sectional view through a commercialtwo-stage forevacuum pump 5 which has been modified for utilisation in amulti-chamber installation. Said forevacuum pump is equipped with anouter casing 28 with an oil sump 29. Accommodated in the outer casing 28is the actual pump 31, a rotary vane vacuum pump 31 with two stages 11and 13. It comprises three discs 32, 33, 34 with pump rings 35, 36accommodated in between. The pump rings 35, 36 form of the pump chambers37, 38, in which there is located one each eccentrically arranged rotor41, respectively 42 with its vanes 43, respectively 44. The rotor 42 islinked to the shaft 45 of a drive motor not depicted. Moreover, thebearing stubs of the rotors 41, 42 are linked to each other in the areaof the disk 33. The diameter of the rotors 41, 42 is equal, theirlengths are different. Thus there result for the two pump stages 11, 13different pumping capacities. When employing the presented pump as atwo-stage vacuum pump with series connected pump stages 11, 13, thelonger pump stage forms the inlet pump stage and the shorter one thedelivery pump stage.

The pump 5 presented has been modified such that the pump stages 11, 13may be operated in parallel. The inlet equipped with an anti-suck backvalve 46 which is present in any case in pumping stage 11 serves asinlet 14. The outlet of pumping stage 11, not depicted in detail, is nolonger linked to the inlet of the pumping stage 13, but instead opensout below the felt hat 47. The pumping stage 13 has been equipped withan independent intake port 48 forming the inlet 16. The intake port 48is linked via pipe section 49 run out of the casing 28 to the pumpchamber 37. The not depicted outlet of this pumping stage 13 also opensout under the felt hat 47. The felt hat 47 serves the purpose of calmingdown the flow and coarsely separating the oil. Further separators whichneed to be connected to the outlets 23 need, compared to thestate-of-the-art, to be present only once.

The invention has been described with reference to the preferredembodiments. Modifications and alterations may occur to others uponreading and understanding the preceding detailed description. It isintended that the invention be constructed as including all suchmodifications and alterations insofar as they come within the scope ofthe appended claims or the eqiuivalents thereof.

1. A multi-chamber installation for treating objects under vacuum,comprising: a forevacuum pump including: a common housing; a pluralityof inlets through the housing, which plurality of inlets are connectedwith a plurality of chambers to be evacuated; a plurality of fluidiclyindependent pumping stages arranged in parallel in the common housing tobe driven together by a common drive, each of said pumping stages beingconnected with one of the inlets, the chambers being evacuated fluidiclyindependently from each other; and at least one outlet for discharginggas from the pumping stages to atmospheric pressure.
 2. The installationaccording to claim 1, wherein the number of chambers and the number ofpumping stages of the forevacuum pump are equal.
 3. The installationaccording to claim 1, wherein the plurality of chambers includes aprocess chamber and at least one pre-chamber linked to the processchamber, the pumping stages of the forevacuum pump having differentpumping capacities, the stage with the highest pumping capacity beingconnected to the process chamber.
 4. The installation according to claim3, further including: a connecting line between the process chamber andan inlet of the corresponding pumping stage; and a high vacuum pumplocated in the connecting line.
 5. The evacuation system according toclaim 4 wherein the high vacuum pump is a turbomolecular vacuum pump. 6.The installation according to claim 1 wherein the forevacuum pumpincludes: a separate rotor for each of the parallel stages, all of therotors being commonly driven and sharing a common oil sump.
 7. Theinstallation according to claim 6 wherein all of the parallel stages areconnected with a common outlet and further including: a single oilseparator connected to the outlet for separating oil from the dischargedgas.
 8. A method for operating a multi-chamber installation for treatingobjects under vacuum, where with the aid of an evacuation system vacuumpressures are produced in a plurality of chambers, the methodcomprising: producing the vacuum pressures with a forevacuum pump with aplurality of pumping stages in a common housing, the common housingbeing equipped with a plurality of inlets, each inlet being connected toone of the chambers and being equipped with a common outlet connected toatmosphere; and operating the pumping stages in parallel.
 9. The methodaccording to claim 8, further including: evacuating the chambers withpumping stages having different pumping capacities.
 10. The methodaccording to claim 9, further including: evacuating a process chamberwith a one of the pumping stages which has the highest pumping capacity.11. The method according to claim 9, further including: evacuating aprocess chamber with a high vacuum pump; and producing a forevacuumpressure required by the high vacuum pump by one of the pumping stages.12. The method according to claim 8 wherein producing the vacuumpressures includes: driving the parallel pump stages in unison with acommon drive, the pumping stages and the common drive being disposed ina common housing.
 13. A multi-stage evacuation system for amulti-chamber installation, the evacuation system including a multistageforevacuum pump, the multistage forevacuum pump having: a plurality ofpumping stages arranged to pump in parallel, a plurality of inlets, eachof the inlets providing a fluidic connection with one chamber of themulti-chamber installation, and an outlet to atmosphere such that thepumping stages of the multistage forevacuum pump operate in parallel todraw vacuum pressures in the chambers.
 14. The evacuation systemaccording to claim 13, further including: a high vacuum pump, one of thestages of the forevacuum pump being connected with the high vacuum pumpfor producing a forevacuum for the high vacuum pump.
 15. The evacuationsystem according to claim 13, wherein the forevacuum pump is a rotaryvane vacuum pump.
 16. In an evacuation system for a multi-chamberinstallation, a multi-stage forevacuum pump comprising: an outer casing;a plurality of pumping stages mounted in the outer casing to pump inparallel, each pumping stage having a separate inlet for connection witha corresponding chamber of the multi-chamber installation, each of theparallel pumping stages having an outlet, which outlets are joinedwithin the casing to define a common outlet, such that the pumpingstages pump gas in parallel from their respective inlets to the commonoutlet; a common oil separator connected with the common outlet.